generic main: add ability to disable timer manager

[tehKaiN]

Description

Adds ability to disable timer manager in generic main code.

I've left it on by default, because currently log blocks depend on it to display time measurements (like they were correct anyway lol). Also, this approach won't break already made games.

Checklist

• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.

[tehKaiN]

no comments? Ok, let's merge it then.